Early Results from the Solar-Minimum 2019 Total Solar Eclipse

We report on first results from our observations in Chile on July 2, 2019, that revealed the extreme-solar-minimum corona, with only equatorial streamers and with visible polar plumes. We have observations in clear skies from our three observing sites: (1) The Cerro Tololo Inter-American Observatory, 7,240-foot altitude, 2 min 6 sec; (2) La Higuera, centerline, 2,500-foot altitude, 2 min 35 sec totality; (3) La Serena, sea level, 2 min 15 sec totality. Prominences on the limb provided orientation and coordination with spacecraft observations from NOAA's GOES-R Solar Ultraviolet Imager (SUVI) and the Atmospheric Imaging Assembly (AIA) on NASA's Solar Dynamics Observatory (SDO). The double-diamond ring at second contact will extend our determination of a new IAU-recommended value of the solar diameter through comparison with models taking into account the precise lunar profile. Our coronal spectra from slitless spectrographs, from CTIO, showed the Fe XIV 530.3 nm green line substantially weaker than the Fe X 637.4 nm red line, corresponding to the relatively low coronal temperature at this phase of the solar-activity cycle. On the spectra we also detected the weak coronal emission line of Ar X at 553.3 nm, as we also detected at the previous total solar eclipse of August 21, 2017, in the USA. We show a comparison of the eclipse observation with a prediction of the structure of the corona from an MHD model, carried out by Predictive Science Inc. (PSI). We consider the lines of sight to NASA's Parker Solar Probe at the times of total eclipses, when we can examine the coronal imaging in terms of electron density to compare with the in situ measurements.

We received major support from grant AGS-903500 from the Solar Terrestrial Program, Atmospheric and Geospace Sciences Division, U.S. National Science Foundation. The CTIO site was courtesy of Associated Universities for Research in Astronomy (AURA). We had additional student support from the Massachusetts NASA Space Grant Consortium; Sigma Xi; the Global Initiatives Fund at Williams College; and the University of Pennsylvania. PSI was supported by AFOSR, NASA, and NSF. ACS received support from the NASA/HGI program, and from the MSFC Hinode project. AV thanks the mathematician Christophoros Mouratidis for his help with the data reduction of the spectra.